Actuators are divided into four main categories, based on their design pattern, and their positions in a particular IoT environment.

#1- Linear actuators

A linear actuator is an actuator that enables an object or element to be moved in a straight line.

#2- Motors

It permits the precise rotation of unit parts or entire objects. There are various types of motors such as servo motors, stepper motor or DC motor (continuous motor rotation).

• Servo motor:

 A servo motor is a rotary actuator or a linear actuator which enables accurate control of angular or linear position, speed and acceleration. It consists of a motor coupled with a sensor for feedback to the location.

• Stepper motor: 

Stepper motors are an electromechanical device which is used for the conversion of electrical power into mechanical power. It is also a synchronous DC brushless motor that is able to split a full rotation into a wide range of discrete steps.

• DC motor (continuous motor rotation): 

The most common actuator used in electronics projects is the Direct Current (DC) motor. It is fast, economical and easy to use. They also come with a wide variety of dimensions to suit different tasks. Basically, electrical DC motors transform electrical energy into mechanical energy. DC motors consist of permanent magnets and loops of wire inside. The wire loops produce a magnetic field, responding to the external field of the static magnets when current is applied.

#3- Relays

A relay is a switch which is electrically controlled. Most relays include electromagnetic actuators for controlling the motor operating power switches in lamps, heaters, AC circuits which themselves can draw much more electrical power or even smart vehicles.

#4- Solenoids

Solenoids transform electrical current into mechanical activity and are thus used as switches very commonly. Solenoids are cheap and are mainly used for on-off applications such as latching, locking and triggering. These also serve as IoT-based gas and water-leak-monitoring controllers.